Coordination polymers are a class of materials which are formed from extended chains, sheets or networks of metal ions interconnected by ligands.
Metal organic frameworks—MOFs—are a type of coordination polymer having extended three dimensional framework structures and show great promise in a wide range of applications including gas storage/release and bacteria/infection control.1 There is particular interest in porous MOFs with accessible coordinatively unsaturated metal sites since these have been shown to greatly enhance the gas storage-release profile.2 For example, such sites are found in the honeycomb-like structure of the CPO-27 family3,4 (or MOF-74).5 These frameworks are constructed from chains of edge-sharing metal-oxygen polyhedra (octahedra when hydrated, square pyramids when dehydrated) connected by 2,5-dihydroxyterephthalate units. The large one-dimensional hexagonal channels permit easy access to the coordinatively unsaturated sites upon activation (dehydration). Indeed, such materials possess excellent adsorption/release profiles for many harmful and biologically active gasses including NO, H2S and CO2.2,6,7 They also show useful antibacterial properties both in their pristine and NO-loaded forms.
Metal organic frameworks possessing porous three-dimensional structures (such as CPO-27) are commonly and traditionally made via solvothermal routes. These approaches have several drawbacks when considering large scale commercial synthesis, including:
1) Use of harmful and environmentally unattractive organic solvents
2) High temperatures and long reaction times resulting in high processing cost
3) Requirement for sealed and pressure-rated vessel
For example, MOFs constructed from chains of edge-sharing metal-oxygen octahedra connected by 2,5-dihydroxyterephthalate units and possessing a honeycomb structure were first reported by Dietzel et al.3 and Rosi et al.5 Both authors used solvothermal techniques to prepare Zn-, Co- and Ni-containing analogues. For example, Dietzel et al. reported the synthesis of Zn-CPO-27 by mixing a solution of 2,5-dihydroxyterephthalic acid in THF with an aqueous solution of Zn nitrate and aqueous sodium hydroxide.4 The resulting mixture was heated in a sealed autoclave at 110° C. for three days. A similar procedure (without sodium hydroxide) was also reported for the Co and Ni analogues.3,4 Rosi et al. employed a similar technique but with DMF as solvent and with a small amount of propanol. Subsequently, the Mg and mixed metal Zn/Co analogues were synthesised in a similar fashion from solutions of the acid linker and metal sources in DMF/water/ethanol and DMF/water solutions, respectively.8,9 
Tranchemontagne et al.10 reported that various MOFs, including Zn-CPO-27, can be made at room temperature and ambient pressure by mixing solutions of the relevant linker and metal source. In one example, MOF-5 (constructed from Zn4O units connected by 1,4-benzenedicarboxylate struts) was prepared by mixing solutions of the linker and Zn acetate in DMF at room temperate and in the presence of triethylamine. Although the amine was added to aid deprotonation of the linker, subsequent studies showed that it was not essential when using Zn. Zn-CPO-27 was synthesised in this way by replacing 1,4-benzenedicarboxylate with 2,5-dihydroxyterephthalic acid (DHTP). While this work removes the requirement for high temperature and pressurised vessels, it should be noted that the syntheses still rely on the use of the environmentally undesirable and hazardous organic solvent DMF.
Similarly, Rosi et al reported the synthesis of Zn-based MOF-69A and -69B at room temperature by dissolving Zn nitrate and linker in DMF/H2O2 with CH3NH2.5 
The Cu-containing MOF HKUST-1 has been shown to form at room temperature either by mixing Cu acetate, 1,3,5-benzenetricarboxylic acid (BTC) and triethylamine in a 1:1:1 mixture of DMF/EtOH/H2O, or by adding a solution of BTC in EtOH to a solution of Cu acetate in H2O/acetic acid.11 
The requirement to use organic solvents in conventional syntheses is dictated by the solubility of the acid linker. For example, 2,5-dihydroxyterephthalic acid is insoluble in water but dissolves in solvents such as THF and trimesic acid is only slightly soluble in water.
A coordination polymer formed between Zn and DHTP but with a different structure to CPO-27 was synthesised by Ghermani et al. at room temperature.12 The material was prepared by adding an aqueous solution of Zn sulphate to the neutralised linker in aqueous sodium hydroxide. However, the resulting structure is composed of linear chains and is non-porous. It is therefore not expected to possess significant gas adsorption capacity.
Akhbari, K. and Morsali, A. J. Iran. Chem. Soc., 2008, 5(1), 48-56 describe the structure and physical characteristics of a Ag(I) trimesate coordination polymer, which is thought to be composed of linear chains. Although it is synthesised at room temperature, the process depends on the use of flammable and toxic methanol. An alternative method of preparation of this material is described by Sun, D., Cao, R., Weng, J., Hong, M. and Liang, Y., J. Chem. Soc., Dalton Trans., 2002, 291-292. The method is a small scale and lengthy lab process not conducive to industrial application.
Methods of synthesising silver MOFs require either high temperatures and pressures (for example, Ding, B., Yi, L., Liu, Y., Cheng, P., Dong, Y-B. and Ma, J-P., Inorg. Chem. Comm., 8, 2005, 38-40) or low temperatures and use of organic solvents (for example, WO 2007/094567 and WO 2007/029902 of Yeong et al.).
It is an object of the present invention to provide a method of MOF synthesis which obviates and/or mitigates one or more of the aforementioned disadvantages.